Electron discharge device and associated circuits



July 18, 1950 A. V. HAEFF ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Original Filed Dec. 8, 1944 5 Sheets-Sheet 1 W BY Mawfifaefi A. V. HAEFF July 18, 1950 ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS 3 Sheets-Sheet 2 Original Filed Dec. 8, 1944 IN V EN TOR. M2102 Jfa 7 July 18, 1950 A. v. HAEFF 2,515,997

ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Original Filed Dec. 8, 1944 3 Sheets-Sheet 3 Patented July 18, 1 950 ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Andrew V. Haeif, Washington, D. 0., assignor to Radio Corporation of America, a corporation of Delaware Original application December 8, 1944, Serial No.

567,226. Divided and this application November 14, 1947, Serial N0. 785,934

My invention relates to electron discharge devices and associated circuits particularly suitable for ultra high frequencies as high power output tubes which are useful as amplifiers or oscillators.

This application is a division'of my copending application, Serial No. 567,226, filed December 8; 1944, now Patent No. 2,507,972 May 16, 1950 and assigned to the same assignee as the present application.

In electron discharge devices intended for high power output and particularly for use at ultra high frequencies, closespacing of the electrodes and high operating voltages are requisites. Op timum operating conditions for maximum output require a maximum instant grid voltage and a minimum instant plate voltage when the peak plate current flows. However, for the usual electron discharge device undesired grid emission due to electron bombardment from the cathode and heating of the grid by radiated heat from the e1ectron collecting surface of the anode or collector may result. Grid and plate circuit loading, burning out of the grid and increasedheating at the anode, which represents wasted energy and hence a lowering of the efficiency of the electron discharge device, may occur under these conditions. In the case of oscillators either self-biasing resistors may be used or fixed bias may be used to obtain the proper biasing voltage on the grid. Where a self biasing resistor is used between grid and cathode, when the grid is positive, electrons strike the grid and cause secondary emission, which results in current flowing in the gridcircuit. This results in a higher positive bias being placed on the grid, thus further increasing the positive grid potential and the velocity of the electrons bombarding the grid. This building up of the positive bias on the grid may cause the grid to burn out. I

In the case' of a fixed bias, while the bias itself does not increase, nevertheless when the gridis at positive peak and the plate voltage is at a mini mum positive voltage, electrons striking the grid cause it to heat up, thus causing emission from 5 Claims. (Cl. 315-6) the grid. Electrons emitted from the grid dura ing the next half cycle, when the gridis negative and the anode positive, cause the electrons from the grid to be accelerated toward the anode'with maximum velocity. These high velocity electrons strike the anode with considerable force and dissipate their energy in heat. Thus, energy is wasted and does not go into the-output as usefulenergy. This grid emission:current, of course, also loads 2 down the plate circuit, another undesirable factor.,

Inorder to minimize grid emission, lower peak grid voltages are required, which as pointed out above means higher plate voltages with lower plate efficiency. It is desirable to have the electrons collected by the plate at a low velocity and to remove the electron receiving surface away fromthe grid to reduce heat absorbed by the grid. But with the usual three-electrode arrangement with the collector anode at a high positive voltage in order to draw the necessary plate current, this is not entirely feasible.

ilt is, therefore, an object-of my invention to a provide, an electron discharge, device having a high power output and which is suitable for use at ultra high frequencies as an amplifier or oscillator.

More specifically, it is another object of my invention to provide an electron discharge device in which grid emission is substantially reduced.

A still further object of my invention is to provide-an electron discharge device in which the electrons may be collected at a low velocity to reduce the energy dissipated-in heat.

These and other objects will appear herein after. l

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the inventime itself will best be understood by reference to the. following description taken in connection with the accompanying drawing in which Fig. 1 is a longitudinal section of an electron discharge device-and associated circuit made according to my invention and Figs. 2, 3, land 5 show longitudinal sections of modifications of the electron discharge device shown in Fig. 1.

' In Fig. 1 I provide an apparatus which can be used as a high power triode amplifier or as an oscillator. It includes an indirectly heated cathode lt followed by a grid H and an anode or collector l2 having cooling fins l2. The envelope is formed by means of the conducting collar member I 3 closed at one end by the cup-shaped insulating member M at its other end by the insulatingcollar member l5 and collector 52 provided with the collar member, 21 sealed to the collar l5. Thecathode heater I0 is provided with a lead 96 extending through-the envelope. The cathode I0 is supported by means of the conductors and leads I8 arranged in a circle around conductor 6 6 and secured at one end to the tubular member |l, theother end of the tubular member ll being secured to'the leads l9 extending throughthe envelope. Members [1, l8 and I9 serve as the other lead for the cathode heater Ill and as the oathode lead. Insulating disc 20 properly centers conductor [6 with respect to tubular member IT. The grid- H is supported by meanstof conducting collar. member 2| secured to thetubular conducting member I3 forming part of the tube envelope, the grid and cathode supports being separated by means of the insulating disc 22. The collector I2 is provided with themember 25.de-. creasing in diameter toward the grid toprotect the seal and provide a proper field for the elec trons. Across the opening iSJpIaced'the'Wire mesh 26 for bringing about the proper field formation through which the electrons pass from the grid to the interior of the collector l2. This has the effect of minimizing eflective transit time between grid and anode.

The input circuit connected between the grid and cathode comprises the outer tubular member 28 electrically connected to thecollarmember l3 and an inner tubular member 29 capacity coupled atits inner end to the element' 32 contacted by thespring-like-elements 30 secured to the cathode leads. The member 32 electrically connected to the elements 30 provides one conductor through which the heating current flows to the cathode heater. The inner conductor I6 is engaged by means of a spring clip member 34 positioned on element 33 capacity coupled to element 32. This arrangement provides means through which the cathode direct current flows to the heater and at the same time provides a path for radio frequency currents. It*will' thus be observed that the grid ll, collar 2|, collar l3. member'28-, member 29,capacity coupling element 32, leads 30 and I 9, tubular member I! and leads l8 provide a coaxial line type resonator cavity circuit completely isolated from other circuits. It is tuned by means of the collar-like element 35 slidably supported on the inner tubularmember 29 by means of the insulator support 35'.

The output circuit includes a drum-like member*'36 electricallyconnected to collar I 3 of the envelope and provided withadisc-like element 31 capacity coupled to the disc-like element'38 positioned transversely of the collar member 21 of the collector l2 and electrically connected thereto. Energy from the output tank circuit is coupled back tothe input circuit by means of the coaxial transmission line comprising inner conductor 39 and outer conductor 40. "This line is made adjustable to insure proper phase relationship of the energy feedbackwith respect to the Voltages in the input circuit, the inner conductor being provided with coupling loops 4i and 42. This adjustable transmission line is'described in greater detail and claimed inmy copending application 'Serial No. 455,175,'=filed August'18, 1942, now Patent No."2,440;089, datedApril 20, 1948, assigned to the same assignee' as the present application. These coupling loops could be made adjustable to control the amount of feedback. This arrangement permits both the input and output circuits to be adjusted independently of each other and for optimum operating conditions. The output is taken by means of loop46 which feeds into the coaxial transmissionline 41.

The transformer w supplies heating current for the cathode heater, and resistor 44 provides the biasing Voltage between the grid and cathode. The anode'or collector voltage is supplied by means of voltage-source 45.

In operation an alternating high frequency voltage-applied between the grid I I and cathode 4 I0 modulates the electron stream passing to the collector l2. The modulated electron stream in passing across th gap between the grid II and the surface of the mesh closure member 26 induces-a voltage in the resonant cavity 36 coupled betweenthegrid and the collector, thus energizing this resonant cavity circuit. Energy is then fed back by means of coupling loop 4!, transmission line 39-40 and coupling loop 42 within the coaxial transmission line acting as the input resonant cavity circuit and comprising members 28- and-29. Tuning of the input circuit is accomplished by means of the tuning collar 35 which may be moved longitudinally of the input circuit. Output may be taken from the resonator 36 by means of the coupling loop 46 and coaxial trans- .mission line 41. In order to feed the energy from the output resonator to the input resonant cavity circuit in proper phase, the length of the transmission line 39-40 may be varied by varying the position of the'movable U-shaped-element 40' of this line to increase or decrease the length of the line.

In the apparatus shown in Fig. 1, the input and output circuits are completely isolated from each other. Due to the fact that electrons are collected at a surface far removed from the grid I I, little radiated heat is absorbed by the grid. This eliminates much of the difiiculty due to grid emission caused by absorption of heat .due to the energy dissipated at the surface of the collector. The large collar-like support 2| for the grid acts as'a means. for conducting heat away from. the grid rapidly to thus further maintain the gridat a low: temperature. In'efiect close spacing of the electrodes is obtained by means of the structure shown without actually. placing the collecting surface close to the grid, thus making the device suitable for use at ultra high frequencies where transit time between the electrodes becomes important. The capacity couplingbetween th output circuit and the anode or collector permits different voltages to be applied to the circuit and the collector and yet at the .same time provides a resonant cavity type of circuit which is particularly suitable for use at ultra high frequencies. The apparatus shown in Fig. 1 can be used either as an amplifier or oscillator by controlling the amount and phase of the energy fed into the input circuit.

In Fig. 2 is shown a modification of the device shown in Fig. 1 and employing ring type seals. The modification shown in' this figure has an added advantage in that the collector may be maintained at a low voltage with respect to some other electrodes within the tube so that the electrons can be collected at a lower velocity than is possible in the apparatus shown in Fig. 1, thus further increasing the efficiency of the tube.

The envelope 50 contains an indirectly heated cathode 5l., grid 52, output and accelerator electrode 53, ring-like secondary electron suppressor 54 and cup-shaped collector. 55. The cathode, grid and accelerator electrodes are supported by means of ring members 56, 51 and 58 sealed through the glass envelope. These ring members provide low loss, low inductance leads for the electrodes and merge into the circuits utilized with the device.

The input circuit comprises a flat'drum-like member 60 electrically connected to the ring 51 and capacitively coupled to the cathode ring'56 by means of the disc-like member 56' electrically connected to the cathode ring 56. The output resonant cavity comprises the drum-like member BI having a wall 62 capacitively coupled to the flat disc-like element 63 electrically connected to the accelerator electrode ring 58. The two circuits are coupled by means of a transmission line formed by an annular-shaped hollow member 64 surrounding the input circuit. Within member 64 is supported the inner conductor 65 having coupling loop 68 positioned within the input circuit and a coupling loop 61 positioned in the output circuit. This transmission line permits in effect a long line occupying a small space.

Cathode heating energy is supplied by means of the transformer 68 and the grid biasing voltage supplied by means of the dropping resistor 89. The collector electrode and suppressor electrode voltages are supplied by means of the voltage source I0, the suppressor being at the lower potential. The output is taken in theusual way 'by loop 6 I With the arrangement shown the accelerator electrode 53 is maintained at a high potential sufiicient to draw a large cathode current. Practically no current is drawn by the accelerator 53 so that little energy is dissipated in this electrode. Collector 55 which is outside the radio frequency circuit may be maintained at a lower potential than would be the case if it acted as an output lectrode and'hence electrons are collected at a lower velocity so that energy wasted as heat is reduced. The input andoutput circuits are completely isolated from each other and the amount of feedback can be controlled as well as its phase by means of the transmission line which can be made adjustable.

In the apparatus shown in Fig. 2 an alternating high frequency voltage applied between cathode I and grid 52 modulates the electron streamfrom cathode 5| and which passes to the accelerator and output electrode 53 and is collected by collector 55, secondaries from 55 being suppressed by electrode 54. The modulated electron stream in passing across the gap between grid 52 and accelerator 53 induces a voltage across the gap, causing energization of the resonator 6|. The accelerator 53 is capacitively coupled by means of' the element 58 and wall 62'of resonator 6|, the radio frequency field being confined within this resonator. The collector, therefore, is external to the radio frequency circuit. The input resonant cavity circuit comprises resonator 6i! electrically connected to the grid 52 through collar 51' and capacitively coupled for radio fre-' quency to the cathode by means of elements 56" and the radially directed ring-like conducting support 56 of the cathode 5|. Energy is fed back into the input circuit by means of the transmission line comprising the loop 61, coil 65 within the annular box-shaped arrangement 64 and loop 66 within the input resonator. This causes the device to operate as an oscillator.

In Fig. 3 is shown a further modification of th construction shown in-Fig. 2 and provided further with an adjustable transmission line for controlling the phase of feedback. In this modification the envelope I5 contains the indirectly heated cathode I5, grid 'I'I, output and accelerator electrode I8, suppressor electrode I9 and collector 88, the cathode heaterbeing supplied through the conductor 8| and conductors 82 mounted in a circle and surrounding the conductor 8| and serving as a support for the cathode. The grid is supported on collar 83, which in turn is supported on leads and support wires 84 mounted in a circle and surrounding conductors 82 and. extending through the envelope of the tube. The

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accelerating electrode is supported by means of radially directed collar 85 connected to and supported by the radially directed ring-like conductor 86 extending through the envelope.

The input circuit comprises the outer tubular member 81 electrically connected to the inner tubular member 88'by means of the closure member 9|. The inner tubular member 88 is capacitively coupled to the collar 89 secured to the outer ends of the-leads and supports 82, the insulating collar 9|] serving to separate members 88 and 89. The input circuit may be tuned by a member 82 slidable longitudinally of the input circuit.

The output tank circuit includes the resonant cavity structure comprising the member 93 and having one wall 9d provided with an outside annular member 95 in which the conducting disc 96 is supported by means of insulating discs 91 and 98. This disc is provided withspring contact engaging members 99 contacting member 85. This construction permits the envelope to be withdrawn from the output tank circuit and disengaged therefrom. Another wall IIID of the resonant cavity is supplied with spring contact members IIII engaging the conductors supporting the grid. The cathode heating circuit includes transformer I06 connected to leads 8i and 82 by spring contact members 8| and 82'. Voltage source I88 supplies accelerator electrode I8 main tained at a higher potential than the collector by means of voltage source I09. Thus, the envelope and its electrodesmay be disengaged from the circuits by pulling the envelope to the right.

Energy may be returned to the input circuit to neutralize input losses or cause the tube to function as an oscillator by means of the transmission line having inner conductor I85 and outer conductor Hi2, one end being provided with coupling loop I83 and the other with coupling loop I04. Intermediate the concentric transmission line is a U-shaped adjustable portion comprising the conductors I85 and I88, which are telescopically engaged with the coaxialline. Thus, by varying the length of this line the phase relationship of the energy fed back from th output circuit to the input circuit can be controlled to insure the desired phase relationship. The output is taken byrneans of coupling loop IID. Otherwise the apparatus functions in a manner similar to that shown in Fig. 2. y

In Figs. 4 and 5 are shownmodifications of the constructions shown in Fig. 3 in which the outside condenser coupling arrangement for th accelerator is avoided. In the arrangement shown in Fig. 4 the envelope IIG encloses the cathode I I I, control'grid I I2, accelerator and output elec-' trode II3, and collector II5 having a mesh conductor I I6 positioned across the opening for providing the proper field between the electrodes. The open end of the collector H5 is telescoped within the output electrode H3 to provide a capacitive coupling therebetween.

The cathode I I I is provided with an inner heater conductor III and outer conductors and leads H8 surrounding conductor III, the input circuit being provided by means of the tubular member I28 capacitively coupled to the outer tubular member I2I by means of the collar I23 having a supporting disc I23 connected between it and the inner tubular member I28. Member I2I is connected to grid leads II2" connected to collar II2ofgridII2.

The output electrode H3 is provided with a radially extending supporting and conducting member IIII electrically connected to the disc I26 closingone end of the tubular'member I24--which is closed at the other end by means of thedisc I25 to provide the output .tanl: circuit of the resonator type connected between the grid and output electrode. The output circuit is energized in. the usual way by inductive effect when the modulated stream of electrons passes across the gap between grid II2 and output electrode H3. Tuning of the input circuit is accomplished by means of the collar member I28 movable longitudinally of the input circuit, and the outputcircult is tuned by means of the collar I26 supported on insulating elements I38 also slidable axially of the output circuit.

Coupling between the input and output circuits is provided by means of the coupling loop I3 I, the output being taken by means of output coupling loop I 32. Cathode heating current is provided by voltage source I33 and proper bias on the grid by means of dropping resistor I34. The collector voltage is supplied by means of voltage source Thus, the electrode I I3, which is maintained at control grid direct current potential, serves to minimize capacitance between the control grid and collector. Large capacitance between the collector and electrode II3 serves to by-pass radio frequency currents. The electron collecting area of the collector is far removed from the control grid and cathode so that the grid may be run quite cool.

In Fig. 5 is shown another arrangement in which the collector may be maintained at a lower positive potential than the output electrode or accelerator. A separate high positively biased electrode is used to get high peak currents. This electrode does not take current. The collector is outside of the radio frequency circuit and has a potential applied only sufiicient to collect the electrons. Thus, there results a high efficiency apparatus of the kind shown in Fig. 3, but without the need of an external capacity coupling arrangement.

In this arrangement the envelope M0 contains the cathode I 58, and grid I60 supported on collar IBI. The output and shielding electrode IE2 is supported by the radially extending support and lead arrangement I63 which extends through the wall of the envelope. The collector I64 is positioned to receive electrons from the cathode, the accelerator electrode I65 being positioned within the output and shielding electrode I62.

The input circuit comprises the outer tubular conductor I connected to the grid leads and supports I6! and the inner tubular member III which is capacitively connected to the cathode leads and support I89. The output circuit comprises the resonant cavity circuit I61 having a wall I65 electrically connected to the radical leads I63 on the output electrode I52 and another wall I66 electrically connected to the tubular member I10. The two circuits are coupled by means of the coupling loop I12. Cathode heating current is supplied by means of transformer I'M through lead I 68 and leads I69 and grid bias voltage by means of voltage source I13. The accelerator and collector voltages are supplied by potential sources I16 and Ill. The output is taken by couplin loop I80.

In the last arrangement described the collector is maintained at a lower potential than the accelerator.

High frequency apparatus made according 'to my invention eliminates or substantially reduces the difficulties due to grid emission. Efiiciencyis increasedby providing means for collecting the electrons at low velocity. This is accomplished while at the same time providing high power outputs whether the apparatus is used as an amplifier 0r oscillator. My apparatus also provides a ready means for disconnecting the electrodes from the associated circuits, thus making available an electron discharge device and an associated circuit apparatus permitting re'ady replacement in case of damage to the tube or where replacement is desired for other reasons.

While I have indicated the preferred embodiments of my'invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

I claim:

1. An electron discharge device having an envelope containing a cathode having radially extending conducting and supporting means extending through the envelope, a grid electrode having radially extendingv conducting and supporting meansextending externally of the envelope, an output electrode positioned adjacent the cathode having conducting means extending radially from the output electrode, all of said radially extending means being sealed through the wall of the envelope, and an electron collector, a cavity resonator having a wall including an element capacitively coupled to the wall of the cavity resonator, said element contacting the radially extending conducting means of said output electrode, said cavity resonator having a wall electrically connecting the cavity resonator to said grid conducting and supporting means, a cavity resonator connected to the grid and capacitively coupled to the cathode, and a transmission line electrically coupling said cavity resonators.

2. An electron discharge device having an envelope containing a cathode, grid, output electrode and'collector, said grid electrode shielding said cathode from said other electrodes, said output electrode comprising a collar-shaped element, said collector being cup-shaped and having its open end capacitively coupled to said output electrode, a cavity resonator electrically coupled between said grid and cathode, and a cavity resonator electrically coupled between said output electrode and said grid.

3. An electron discharge device having an envelope containing a cathode, grid, output electrode and collector, said grid electrode surrounding and shielding said cathode from said other electrodes, said output electrode comprising a collar-shaped element, said collector being cupshaped and having its open end capacitively coupled to said output electrode, said output electrode being provided with radially extending supporting and conducting means extending through the wall of the envelope, a cavity resonator electrically coupled between said grid and cathode, a cavity resonator electrically coupled between said output electrode and said grid, and means for coupling said cavity resonators.

4. An electron discharge device having an ,envelope containing a cathode, grid, output electrode .and collector, said grid electrode surrounding and shielding said cathode from said other electrodes, said output electrode comprising a collar-shaped element, an accelerator electrode within said output electrode in said envelope, said output electrode being provided with a radially extending supporting and conducting means extending through the wall of the envelope, a cavity resonator electrically coupled between said grid and cathode, and a cavity resonator electrically coupled between said output electrode and said grid.

5. An electron discharge device having an, envelope containing a cathode. grid, output electrode and collector, said grid electrode being formed to surround and shield said cathode from said other electrodes, said output electrode comprising a collar-shaped element, a collarshaped accelerator electrode within said output electrode in said envelope, said output electrode being provided with a radially extending supporting and conducting means extending through the wall of the envelope, a cavity resonator electrically coupled between said grid and cathode, a cavity resonator electrically coupled between said output electrode and said grid, and means for coupling said cavity resonators.

ANDREW V. HAEFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 2,396,802 Mouromtseff et al. Mar. 19, 1946 2,408,809 Pierce Oct. 8, 1946 2,425,748 Llewellyn Aug. 19, 1947 

